A gerotor is a widely used pumping mechanism that utilizes a pair of meshed gears in a chamber to create a pumping action to pump various liquids (e.g., oil). One of the gears is an inner gear with outer gear teeth, and the other gear is an outer gear with inner gear teeth. The inner gear has one less gear tooth than the outer gear. The offset created by the feature(s) of the inner gear in relation to the outer gear establishes a cavity between the gears. When the inner gear is rotated, the cavity between the teeth opens through half of a revolution and closes through the other half. The opening and closing of the cavity facilitates a pumping action whereby liquid may be drawn into the cavity through a channel during the opening phase and liquid is discharged from the cavity through another channel during the closing phase.
Previous solutions of assembling gerotors included permanently securing the pump shaft to an inner gear, for example, by welding the two parts together. While welding methods may provide a secure union, they suffer from several disadvantages. Welding the pump shaft and inner gear together is a fairly expensive and time-consuming assembly process. Further, welding can result in varying quality of the connection and may increase the opportunity for manufacturing defects. Additionally, welding requires extra materials and machinery.
Further, several less permanent methods have been used as well, such as coupling a pump shaft notch and an inner gear notch by inserting a single key that engages both notches. Using a separate key also has several disadvantages, for example, the key is a separate loose part that only provides limited rotational securing. Rotational securing is provided only while the key is maintained in the pump shaft and inner gear notches, and while the pump shaft is not subject to substantial axial movement with respect to the inner gear. Therefore, a separate additional means for securing the pump shaft axially to the inner gear would be required. Additionally, these prior methods of assembly result in a gerotor that is difficult to assemble, to disassemble and to repair.
For at least these reasons, therefore, it would be advantageous to provide a new gerotor assembly and methods for assembling a gerotor. Further, it would be desirable if, in at least some embodiments, such gerotors and assembly methods could be implemented at a reduced cost and required less time to implement relative to prior solutions. Additionally, it would be advantageous to provide a new gerotor that can, in at least some embodiments, be assembled with a lower opportunity for manufacturing defects and with less individual parts. Further, it would be advantageous to provide a new gerotor that allows, in at least some embodiments, for efficient and predictable disassembly of the pump shaft and inner rotor.